Building an undo log for in-memory blocks of data

ABSTRACT

Provided are techniques for building an undo log for in-memory blocks of data. Permission on a block of data in memory is set to prevent updates to that block of data using a memory protection function. In response to an update operation attempting to update the block of data in the memory, an interrupt with a location of the block of data is received, the block of data is copied to an undo log entry in an undo log, and the permission on the block of data in the memory is set to allow the update to that block of data to proceed using the memory protection function.

FIELD

Embodiments of the invention relate to building an undo log forin-memory blocks of data.

BACKGROUND

In-memory databases typically have the following characteristics: (1)most, if not all, data fits into memory, (2) most updates are applied inbatch operations, and (3) most updates are appends of new data.

The data may be stored using any technique, such as relational orcolumnar.

When the update process is interrupted or aborted, the changes made todata in-memory need to be undone to keep the database consistent.

Most database systems use transaction logging, in which each individualupdate is logged, and, if the transaction is interrupted or aborted, theundo log is applied to roll back each individual change.

Some database systems may utilize a page tracking system (bufferpool) orintercept all updates at the application layer and perform unlogoperations.

SUMMARY

Provided are a method, computer program product, and system for buildingan undo log for in-memory blocks of data. Permission on a block of datain memory is set to prevent updates to that block of data using a memoryprotection function. In response to an update operation attempting toupdate the block of data in the memory, an interrupt with a location ofthe block of data is received, the block of data is copied to an undolog entry in an undo log, and the permission on the block of data in thememory is set to allow the update to that block of data to proceed usingthe memory protection function.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 illustrates, in a block diagram, a computing environment inaccordance with certain embodiments.

FIG. 2 illustrates, in a flow diagram, operations for logging in-memoryupdates in accordance with certain embodiments.

FIG. 3 illustrates, in a flow diagram, processing of an undo log inaccordance with certain embodiments.

FIG. 4 depicts a cloud computing node in accordance with certainembodiments.

FIG. 5 depicts a cloud computing environment in accordance with certainembodiments.

FIG. 6 depicts abstraction model layers in accordance with certainembodiments.

DETAILED DESCRIPTION

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

Some operating systems provide a memory protection function (e.g.,mprotect( )). Embodiments use the operating system's memory protectionfunction to identify changed blocks of data in-memory for the purpose ofbuilding an undo log that can be used to restore the blocks of data inthe event of an abort of the transaction that applied the update to theblocks of data.

FIG. 1 illustrates, in a block diagram, a computing environment inaccordance with certain embodiments. A computing device 100 includes oneor more applications 110, an in-memory undo log engine 120, memory 130,and operating system 140. The computing device 100 includes an undo log122. The memory 130 stores blocks of data 132. The operating system 140provides a memory protection function 142. The computing device 100 iscoupled to data store 150, which includes blocks of data 160. Blocks ofdata in the memory 130 may be transferred to the data store 150 forstorage. In certain embodiments, the data store 150 is part of thecomputing device 100. In alternative embodiments, the data store 150 isexternal to (and separate from) the computer device 100.

FIG. 2 illustrates, in a flow diagram, operations for logging in-memoryupdates in accordance with certain embodiments. Control begins at block200 with the in-memory undo log engine 120 setting a permission on ablock of data in memory to prevent updates to that block of data using amemory protection function. In certain embodiments, the permission isset to one value to block write access and set to another value to allowwrite access to the block of data in the memory. In certain embodiments,an update operation may be a modify operation that changes the block ofdata in memory, a delete operation that deletes the block of data frommemory or an insert operation that inserts (adds) the block of data tomemory. In certain embodiments, the block of data is part of a page ofmemory. In block 202, the in-memory undo log engine 120, in response toan update operation attempting to update the block of data in memory,receives an interrupt with a location of the block of data. In block204, the in-memory undo log engine 120 copies the block of data to anundo log entry in an undo log. In block 206, the in-memory undo logengine 120 sets the permission on the block of data in memory to allowupdates to that block of data using the memory protection function.

FIG. 3 illustrates, in a flow diagram, processing of an undo log inaccordance with certain embodiments. Control begins at block 300 withthe in-memory undo log engine 120 determining whether a transaction(batch operation) that included the update operation for a block of dataassociated with an undo log entry has committed. If so, processingcontinues to block 302, otherwise, processing continues to block 304. Inblock 302, the in-memory undo log engine 120 removes the associated undolog entry from the undo log. In block 304, the in-memory undo log engine120 sets the permission on the block of data in memory to block updatesto that block of data (e.g., sets the permission to read-only to blockwrite access). In block 306 (because the transaction did not commit(e.g., the transaction failed)), the in-memory undo log engine 120 usesthe associated undo log entry from the undo log to undo updates of theupdate operation (e.g., by copying the block of data from the undo logentry back to the memory). From block 306, processing continues to block304.

The in-memory undo log engine 120 exploits the memory protectionfunction (e.g., mprotect( )), which is an operating system mechanismthat allows pages of memory to be marked with specific characteristics,including blocking write access to the specific memory page or range ofpages) in order to track updates to the blocks of data. When a writeprotected page of data is updated, the operating system generates aninterrupt (e.g., a segmentation fault (seg fault)). Thus, the in-memoryundo log engine 120 uses faults to actually generate the contents of theundo log. The interrupt information includes a location (e.g., anaddress) of the block of data that an application was attempting toupdate. That location may be mapped to a specific portion of data. Aspart of the interrupt handling, the in-memory undo log engine 120 copiesthe block of data prior to the update to an undo log. Then, the memorypage protection will be relaxed and the update will be allowed toproceed. If the transaction applying the update is aborted, the undo logis applied to restore the block of data back to its original state.

In certain embodiments, the actual number of updates that are done isrelatively small compared to the amount of new blocks of data that areappended. Embodiments only log the updates of existing blocks of data,while newly appended pages do not need to be logged because typicallythe catalogs controlling the blocks of data will not reflect the newlyadded blocks of data until the transaction commits. The same mechanismprotecting the updated blocks of data also protects the catalogs whenthey are updated with information about the newly appended blocks ofdata.

In certain embodiments, database engines use memory mapped (mmap) filesto store blocks of data in memory. These database engines allow forappends of new blocks of data to existing tables. The append of the newblocks of data happens in batch operations (which may also be referredto as transactions), where multiple tables are updated by a single batchoperation. Once the batch operation completes, the tables are hardened(copied) to the data store (e.g., disk) (e.g., using an msync( )operation). When blocks of data are stored in a mmap file, theapplication has little control over when updated blocks of data areflushed to the data store. The in-memory undo log engine 120 providesrecoverability of blocks of data in the event of a unplanned outage byproviding recoverability of those updated blocks of data that theoperating system independently chooses to flush to the data store whilein the midst of the transaction.

The mmap file may have memory protection semantics applied to that mmapfile. When an update is applied to the mmap file, an interrupt isgenerated containing the location of the violation (of the protectionsemantics). The in-memory undo log engine 120 translates the locationinto a specific block of data within the mmap file. The in-memory undolog engine 120 saves that block of data to an undo log and releases theprotection of the block of data, allowing the update to complete. Whenthe transaction is complete, the in-memory undo log engine 120 flushesthe undo log. At periodic times, the mmap file may be flushed, mprotectturned back on, and the undo removed.

In certain embodiments, the in-memory undo log engine 120 builds an undolog for in-memory databases. In certain embodiments, the in-memory undolog engine 120 exploits the use of the operating system mechanismmprotect( ) to identify changed blocks of data in an in-memory databasefor the purpose of building an undo log that can be used to restore theblocks of data in the event of the abort of the transaction that appliedthe update. In such embodiments, the in-memory undo log engine 120exploits the mprotect( ) function in order to track changes to theblocks of data, enabling the operating system to generate a segmentationfault (seg fault), such that the interrupt information includes theoffending address (that address can be mapped to a specific portion of apage in memory, such as a block of data). As part of the interrupthandling, the in-memory undo log engine 120 logs a copy of the block ofdata prior to the update to an undo log, relaxes the memory pageprotection, and allows the update to proceed. With these embodiments, ifthe transaction applying the update is aborted, the undo log is appliedto restore the block of data back to its original state.

Cloud Environment

It is understood in advance that although this disclosure includes adetailed description on cloud computing, implementation of the teachingsrecited herein are not limited to a cloud computing environment. Rather,embodiments of the present invention are capable of being implemented inconjunction with any other type of computing environment now known orlater developed.

Cloud computing is a model of service delivery for enabling convenient,on-demand network access to a shared pool of configurable computingresources (e.g. networks, network bandwidth, servers, processing,memory, storage, applications, virtual machines, and services) that canbe rapidly provisioned and released with minimal management effort orinteraction with a provider of the service. This cloud model may includeat least five characteristics, at least three service models, and atleast four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provisioncomputing capabilities, such as server time and network storage, asneeded automatically without requiring human interaction with theservice's provider.

Broad network access: capabilities are available over a network andaccessed through standard mechanisms that promote use by heterogeneousthin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to servemultiple consumers using a multi-tenant model, with different physicaland virtual resources dynamically assigned and reassigned according todemand. There is a sense of location independence in that the consumergenerally has no control or knowledge over the exact location of theprovided resources but may be able to specify location at a higher levelof abstraction (e.g., country, state, or datacenter).

Rapid elasticity: capabilities can be rapidly and elasticallyprovisioned, in some cases automatically, to quickly scale out andrapidly released to quickly scale in. To the consumer, the capabilitiesavailable for provisioning often appear to be unlimited and can bepurchased in any quantity at any time.

Measured service: cloud systems automatically control and optimizeresource use by leveraging a metering capability at some level ofabstraction appropriate to the type of service (e.g., storage,processing, bandwidth, and active user accounts). Resource usage can bemonitored, controlled, and reported providing transparency for both theprovider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer isto use the provider's applications running on a cloud infrastructure.The applications are accessible from various client devices through athin client interface such as a web browser (e.g., web-based email). Theconsumer does not manage or control the underlying cloud infrastructureincluding network, servers, operating systems, storage, or evenindividual application capabilities, with the possible exception oflimited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer isto deploy onto the cloud infrastructure consumer-created or acquiredapplications created using programming languages and tools supported bythe provider. The consumer does not manage or control the underlyingcloud infrastructure including networks, servers, operating systems, orstorage, but has control over the deployed applications and possiblyapplication hosting environment configurations.

Infrastructure as a Service (IaaS): the capability provided to theconsumer is to provision processing, storage, networks, and otherfundamental computing resources where the consumer is able to deploy andrun arbitrary software, which can include operating systems andapplications. The consumer does not manage or control the underlyingcloud infrastructure but has control over operating systems, storage,deployed applications, and possibly limited control of select networkingcomponents (e.g., host firewalls).

Deployment Models are as follows:

Private cloud: the cloud infrastructure is operated solely for anorganization. It may be managed by the organization or a third party andmay exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by severalorganizations and supports a specific community that has shared concerns(e.g., mission, security requirements, policy, and complianceconsiderations). It may be managed by the organizations or a third partyand may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the generalpublic or a large industry group and is owned by an organization sellingcloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or moreclouds (private, community, or public) that remain unique entities butare bound together by standardized or proprietary technology thatenables data and application portability (e.g., cloud bursting for loadbalancing between clouds).

A cloud computing environment is service oriented with a focus onstatelessness, low coupling, modularity, and semantic interoperability.At the heart of cloud computing is an infrastructure comprising anetwork of interconnected nodes.

Referring now to FIG. 4, a schematic of an example of a cloud computingnode is shown. Cloud computing node 410 is only one example of asuitable cloud computing node and is not intended to suggest anylimitation as to the scope of use or functionality of embodiments of theinvention described herein. Regardless, cloud computing node 410 iscapable of being implemented and/or performing any of the functionalityset forth hereinabove.

In cloud computing node 410 there is a computer system/server 412, whichis operational with numerous other general purpose or special purposecomputing system environments or configurations. Examples of well-knowncomputing systems, environments, and/or configurations that may besuitable for use with computer system/server 412 include, but are notlimited to, personal computer systems, server computer systems, thinclients, thick clients, handheld or laptop devices, multiprocessorsystems, microprocessor-based systems, set top boxes, programmableconsumer electronics, network PCs, minicomputer systems, mainframecomputer systems, and distributed cloud computing environments thatinclude any of the above systems or devices, and the like.

Computer system/server 412 may be described in the general context ofcomputer system executable instructions, such as program modules, beingexecuted by a computer system. Generally, program modules may includeroutines, programs, objects, components, logic, data structures, and soon that perform particular tasks or implement particular abstract datatypes. Computer system/server 412 may be practiced in distributed cloudcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed cloud computing environment, program modules may be locatedin both local and remote computer system storage media including memorystorage devices.

As shown in FIG. 4, computer system/server 412 in cloud computing node410 is shown in the form of a general-purpose computing device. Thecomponents of computer system/server 412 may include, but are notlimited to, one or more processors or processing units 416, a systemmemory 428, and a bus 418 that couples various system componentsincluding system memory 428 to processor 416.

Bus 418 represents one or more of any of several types of busstructures, including a memory bus or memory controller, a peripheralbus, an accelerated graphics port, and a processor or local bus usingany of a variety of bus architectures. By way of example, and notlimitation, such architectures include Industry Standard Architecture(ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA)bus, Video Electronics Standards Association (VESA) local bus, andPeripheral Component Interconnects (PCI) bus.

Computer system/server 412 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 412, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 428 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 430 and/or cachememory 432. Computer system/server 412 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 434 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 418 by one or more datamedia interfaces. As will be further depicted and described below,memory 428 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 440, having a set (at least one) of program modules 442,may be stored in memory 428 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. Program modules 442 generally carry out the functionsand/or methodologies of embodiments of the invention as describedherein.

Computer system/server 412 may also communicate with one or moreexternal devices 414 such as a keyboard, a pointing device, a display424, etc.; one or more devices that enable a user to interact withcomputer system/server 412; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 412 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 422. Still yet, computer system/server 412can communicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 420. As depicted, network adapter 420communicates with the other components of computer system/server 412 viabus 418. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 412. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

Referring now to FIG. 5, illustrative cloud computing environment 550 isdepicted. As shown, cloud computing environment 550 comprises one ormore cloud computing nodes 410 with which local computing devices usedby cloud consumers, such as, for example, personal digital assistant(PDA) or cellular telephone 554A, desktop computer 554B, laptop computer554C, and/or automobile computer system 554N may communicate. Nodes 410may communicate with one another. They may be grouped (not shown)physically or virtually, in one or more networks, such as Private,Community, Public, or Hybrid clouds as described hereinabove, or acombination thereof. This allows cloud computing environment 550 tooffer infrastructure, platforms and/or software as services for which acloud consumer does not need to maintain resources on a local computingdevice. It is understood that the types of computing devices 554A-Nshown in FIG. 5 are intended to be illustrative only and that computingnodes 410 and cloud computing environment 550 can communicate with anytype of computerized device over any type of network and/or networkaddressable connection (e.g., using a web browser).

Referring now to FIG. 6, a set of functional abstraction layers providedby cloud computing environment 550 (FIG. 5) is shown. It should beunderstood in advance that the components, layers, and functions shownin FIG. 6 are intended to be illustrative only and embodiments of theinvention are not limited thereto. As depicted, the following layers andcorresponding functions are provided:

Hardware and software layer 660 includes hardware and softwarecomponents. Examples of hardware components include mainframes, in oneexample IBM® zSeries® systems; RISC (Reduced Instruction Set Computer)architecture based servers, in one example IBM pSeries® systems; IBMxSeries® systems; IBM BladeCenter® systems; storage devices; networksand networking components. Examples of software components includenetwork application server software, in one example IBM WebSphere®application server software; and database software, in one example IBMDB2® database software. (IBM, zSeries, pSeries, xSeries, BladeCenter,WebSphere, and DB2 are trademarks of International Business MachinesCorporation registered in many jurisdictions worldwide).

Virtualization layer 662 provides an abstraction layer from which thefollowing examples of virtual entities may be provided: virtual servers;virtual storage; virtual networks, including virtual private networks;virtual applications and operating systems; and virtual clients.

In one example, management layer 664 may provide the functions describedbelow. Resource provisioning provides dynamic procurement of computingresources and other resources that are utilized to perform tasks withinthe cloud computing environment. Metering and Pricing provide costtracking as resources are utilized within the cloud computingenvironment, and billing or invoicing for consumption of theseresources. In one example, these resources may comprise applicationsoftware licenses. Security provides identity verification for cloudconsumers and tasks, as well as protection for data and other resources.User portal provides access to the cloud computing environment forconsumers and system administrators. Service level management providescloud computing resource allocation and management such that requiredservice levels are met. Service Level Agreement (SLA) planning andfulfillment provide pre-arrangement for, and procurement of, cloudcomputing resources for which a future requirement is anticipated inaccordance with an SLA.

Workloads layer 666 provides examples of functionality for which thecloud computing environment may be utilized. Examples of workloads andfunctions which may be provided from this layer include: mapping andnavigation; software development and lifecycle management; virtualclassroom education delivery; data analytics processing; transactionprocessing; and in-memory undo log processing.

Thus, in certain embodiments, software or a program, implementingin-memory undo log processing in accordance with embodiments describedherein, is provided as a service in a cloud environment.

In certain embodiments, the computing device 100 has the architecture ofcomputing node 410. In certain embodiments, the computing device 100 ispart of a cloud environment. In certain alternative embodiments, thecomputing device 100 is not part of a cloud environment.

Additional Embodiment Details

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, solid state memory, magnetic tape orany suitable combination of the foregoing. In the context of thisdocument, a computer readable storage medium may be any tangible mediumthat can contain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the embodiments of the invention are described below withreference to flowchart illustrations and/or block diagrams of methods,apparatus (systems) and computer program products according toembodiments of the invention. It will be understood that each block ofthe flowchart illustrations and/or block diagrams, and combinations ofblocks in the flowchart illustrations and/or block diagrams, can beimplemented by computer program instructions. These computer programinstructions may be provided to a processor of a general purposecomputer, special purpose computer, or other programmable dataprocessing apparatus to produce a machine, such that the instructions,which execute via the processor of the computer or other programmabledata processing apparatus, create means for implementing thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational processing (e.g., operations or steps) to beperformed on the computer, other programmable apparatus or other devicesto produce a computer implemented process such that the instructionswhich execute on the computer or other programmable apparatus provideprocesses for implementing the functions/acts specified in the flowchartand/or block diagram block or blocks.

The code implementing the described operations may further beimplemented in hardware logic or circuitry (e.g., an integrated circuitchip, Programmable Gate Array (PGA), Application Specific IntegratedCircuit (ASIC), etc. The hardware logic may be coupled to a processor toperform operations.

Devices that are in communication with each other need not be incontinuous communication with each other, unless expressly specifiedotherwise. In addition, devices that are in communication with eachother may communicate directly or indirectly through one or moreintermediaries.

A description of an embodiment with several components in communicationwith each other does not imply that all such components are required. Onthe contrary a variety of optional components are described toillustrate the wide variety of possible embodiments of the presentinvention.

Further, although process steps, method steps, algorithms or the likemay be described in a sequential order, such processes, methods andalgorithms may be configured to work in alternate orders. In otherwords, any sequence or order of steps that may be described does notnecessarily indicate a requirement that the steps be performed in thatorder. The steps of processes described herein may be performed in anyorder practical. Further, some steps may be performed simultaneously.

When a single device or article is described herein, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described herein (whether ornot they cooperate), it will be readily apparent that a singledevice/article may be used in place of the more than one device orarticle or a different number of devices/articles may be used instead ofthe shown number of devices or programs. The functionality and/or thefeatures of a device may be alternatively embodied by one or more otherdevices which are not explicitly described as having suchfunctionality/features. Thus, other embodiments of the present inventionneed not include the device itself.

The illustrated operations of the flow diagrams show certain eventsoccurring in a certain order. In alternative embodiments, certainoperations may be performed in a different order, modified or removed.Moreover, operations may be added to the above described logic and stillconform to the described embodiments. Further, operations describedherein may occur sequentially or certain operations may be processed inparallel. Yet further, operations may be performed by a singleprocessing unit or by distributed processing units.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, “the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the present invention(s)” unless expressly specifiedotherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of embodiments of the present invention has been presentedfor purposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The embodiments were chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

The foregoing description of embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the embodiments to the preciseform disclosed. Many modifications and variations are possible in lightof the above teaching. It is intended that the scope of the embodimentsbe limited not by this detailed description, but rather by the claimsappended hereto. The above specification, examples and data provide acomplete description of the manufacture and use of the composition ofthe embodiments. Since many embodiments may be made without departingfrom the spirit and scope of the invention, the embodiments reside inthe claims hereinafter appended or any subsequently-filed claims, andtheir equivalents.

1. A method, comprising: setting, using a processor of a computer, apermission on a block of data in memory to prevent updates to that blockof data using a memory protection function; in response to an updateoperation attempting to update the block of data in the memory,receiving an interrupt with a location of the block of data; copying theblock of data to an undo log entry in an undo log; and setting thepermission on the block of data in the memory to allow the update tothat block of data to proceed using the memory protection function. 2.The method of claim 1, further comprising: in response to determiningthat a transaction that included the update operation has failed, usingthe associated undo log entry to restore the block of data; and settingthe permission on the block of data in the memory to block updates tothat block of data.
 3. The method of claim 1, further comprising: inresponse to determining that a transaction that included the updateoperation for the block of data has committed, removing the associatedundo log entry from the undo log; and setting the permission on theblock of data in the memory to block updates to that block of data. 4.The method of claim 1, wherein the memory protection function allowspages of memory to be marked with characteristics, and wherein one ofthe characteristics is blocking write access to the pages of memory. 5.The method of claim 1, wherein a transaction updates multiple tables inthe in-memory database.
 6. The method of claim 1, wherein the memorystores an in-memory database.
 7. The method of claim 1, wherein softwareis provided as a service in a cloud environment. 8-21. (canceled)